662 



MK JOHN AITKEN ON THE NUMBER OF DUST PARTICLES IN THE 



It was thought it mii>ht be interesting to see how far the Callievar observations were 

 supported by other high-level observations. The Rigi Kulm observations have therefore 

 been reduced to tables, in the same manner as the other observations, and the results 

 will be found in Tables XIX., XX. and XXI. Unfortunately, all the Rigi observations 

 are not suitable for this purpose, but all of them taken when estimates of haze were 

 made and the conditions fairly steady have been used. High numbers due to the daily 

 maximum, calms, &c, were omitted. From these last tables it will be seen that when 



Table XIX. — Showing the Relation between the Number of Bast Particles and the Transparency 

 of the Atmosphere on the Rigi Kulm when the Wet-Bulb Bepression was between 2° and 4°. 



Date. 



Lowest 

 Number. 



Highest 

 Number. 



Mean 

 Number. 



Limit of 



Visibility in 



Miles. 



c. 



19th May 1891 

 22nd „ 1889 

 16th „ 1893 



428 



434 



1225 



690 



850 



2600 



559 



642 



1912 



150 



100 

 40 



83 ' 850 ) Mean 

 64,200 > 4 i - ' 



77^80 f' 5 ' 1 ' 6 



Table XX. — Showing the Relation between the Number of Bust Particles and the Transparency 

 of the Atmosphere on the Rigi Kulm ivhen the Wet-Bulb Bepression ivas between 4° and 7°. 



Date. 



Lowest 

 Number. 



Highest 

 Number. 



Mean 

 Number. 



Limit of 



Visibility in 



Miles. 



C. 



23rd May 1891. 

 15th „ 1893. 

 23rd „ 1892. 



478 



925 



1350 



535 



1375 

 1425 



506 

 1150 

 1387 



200 



100 



70 



101 ' 20 °1 Mean 

 115,000 J^Ttf^n 



97 090 J 104 ' 430 



Table XXI. — Showing the Relation between the Number of Bust Particles and the Transparency 

 of the Atmosphere on the Rigi Kulm when the Wet-Bulb Bepression was 7° and over. 



Date. 



Lowest 

 Number. 



Highest 

 Number. 



Mean 

 Number. 



Limit of 



Visibility in 

 Miles. 



C. 



21st May 1891 . 



378 



458 



418 



200 



83,6001 





20th „ „ 







326 



683 



505 



150 



75,750 





21th „ 1889 







350 



685 



517 



250 



129,250 





>i >> >> 







5:52 



580 



556 



250 



139,000 



Mean, 

 '124,211 



19th „ 1890 







375 



775 



575 



250 



143,750 



23rd „ 1889 







515 



1100 



807 



200 



161,400 





25th „ 1892 







843 



850 



846 



140 



118,440 





14th „ 1893 







1100 



1750 



1425 



100 



142,500 J 





